Cleft lip and palate (CL/P) is a major congenital structural anomaly that is notable for significant lifelong morbidity and complex etiology. The extensive psychological, surgical, speech and dental involvement emphasize the importance of understanding the underlying causes. Cleft lip and palate, like other complex diseases, provides a challenge in determining the multiple genetic, stochastic, and environmental factors that lead to its phenotype. In this proposal, the P.I. will pursue the complex causes of cleft lip and palate through investigations of a genetic form of clefting, Van der Woude syndrome (VDWS). VDWS is an excellent model of the more than 300 syndromic forms of CL/P. VDWS is the most prevalent syndromic form of CL/P and its clinical presentation is most similar to nonsyndromic classes. The main goal of this proposal is to discover the structure and function of the VDWS gene. A more long-term goal is to identify gene-gene and gene-environment interactions. These goals will be achieved with the following experiments: 1) Identification of the VDWS gene. A Taqman assay will be used to screen for disease-causing microdeletions that may further restrict the region that contains the VDWS gene. Gene-finding techniques, including the sequence analysis of the entire 600 kb critical region, will be used to identify transcriptional units. Mutation screens will be used to find disease-causing changes in the DNA. 2) Characterization of the VDWS gene and its mouse homologue, including complete cDNA and genomic sequence analysis, the study of temporal and tissue-specific expression to identify developmental pathways that require the VDWS gene function and screens for gene homologues which may function in the same pathway 3) identification of sequences that regulate VDWS gene expression and the development of transgenic mouse models, including a mouse knockout that will be used in 4) long-term studies that will include complementation experiments to identify other genes in the pathway and investigate the effects of environmental factors on the VDWS gene.